Flotation of niobium-bearing minerals



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IN YEN TORS J.A. Roland FAUCHER Si/fen DESSUREAUX ATTORNEYS PatentedNov. 8, 1966 ice 2,959,281 FLOTATION OF NIOBIUM-BEARI NG MINERALS J. A.Roland Faucher and Silicn Dessureaux, Montreal, Quebec, Canada,assignors to Technical Managers Inc., West, Montreal, Quebec, CanadaFiled Dec. 31, 1958, Ser. No. 784,391

15 Claims. Cl. 209-12) This invention relates to the beneficiation byfroth flotation of the niobium-bearing minerals (niobates) from theirores. More particularly, it is concerned with the separation ofniobium-bearing minerals, such as pyrochlore, perovskite, niocalite,betafite and the like, from the other constituents of their ores.

The typical problems involved as well as their solutions are found inthe production of pyrochlore concentrates.

Up to a relatively recent date, niobium, also known as columbium, wasconsidered as a rather rare constituent of the earths crust. This hasprevented a wide-spread use of the element which was rather costly. Thediscovery of large deposits of pyrochlorebearing rocks in various partsof the world will lead the industry into a larger use of niobium sincethere is no more risk of a lack of production.

Niobium ores being much more abundant than anticipated will cause theprice of the element to decrease and this also will promote furtherusage. There is no doubt that pyrochlore ore Will eventually become themajor source of niobium.

The main usage of niobium is in the manufacture of high-temperaturealloys which become more and more essential in this age ofjet'propulsion and rocket missiles. Niobium in addition, stands a goodchance of being used in atomic piles on account of its high corrosionand temperature resistance, coupled with good structural behaviour.

In commercial, practice, the use of niobium oxides, ferro-niobium andniobium .metal has become increasingly important and, accordingly, thedemand for high grade concentrates from which they may be recovered hassteadily increased. Unfortunately, while there are large naturaldeposits of niobium minerals, the grade of these ores in most cases isnot sufficiently high to make recovery of niobium therefrom commerciallyfeasible, and no process has been available for readily and effectivelyproducing concentrates of niobium-bearing minerals sufficiently rich inNb to be commercial.

Particularly is this true of most pyrochlore deposits within Canada andelsewhere in the world. Therefore, while the process is not limitedthereto, the invention will be illustrated by its application to niobiumores-and pyrochlores in particular.

Natural deposits of niobium-bearing minerals are usually orescontaining, in addition to the niobium-bearing minerals, such aspyrochlore, perovskite, niocalite, betafite and the like, a mixed ganguecomposed of carbonates, phosphates, mica, ironymincrals, silicates, etc.Such a mixed gangue may be comprised, for instance, of calcite, apatite,biotite, magnetite and pyroxene, and also metallic sulphides such asprite, pyrrhotite, sphalerite and galena. The proportions of the variousconstituents of gangue may, of course, varyconsiderably depending on theorigin of the ore. Ordinarily, this mixed gangue content must be'reducedto produce a concentrate meeting commercial standards, forexampleto beused as raw 2 material for the production of niobium metal or salts, andferro-niobium.

It is, therefore, the principal object of the present invention toprovide a sequence of operations and a process by which a concentratesatisfactorily high in Nb O content can be obtained. It is also anobject to provide a process whereby this is accomplished in aneconomical manner and with good recovery. It is a further object toprovide suitable reagents for use in this process, which reagents aresimple in use, readily obtainable and effective in operation.

It is with the increase in the Nb O assay that the present invention isprimarily concerned. This problem has been extremely difficult to solve,mainly because the niobium-bearing minerals, with which this inventionis concerned, have been considered either as non-floatable or as havinga very low floatability index. Moreover, the problem was complicated bythe absence of knowledge of a selective depressant for theniobium-bearing minerals when attempts were made to increase the Nb O ofthe ore by removing by flotation some of the gangue constituents.

In accordance with the main characteristic of the present invention, ithas been found that the niobium bearing minerals can be floated with agood separation from the remaining gangue constituents by means of acationic promoter of the amine type, and a selective activator for theniobium bearing minerals containing a source of free ions selected fromthe group consisting of fluoride and fiuosilicate ions, the frothflotation being carried out in an acidic circuit. Preferably thecationic promoter is selected from mono-amine and di-amine acetates andheterocyclic organic amines. The source of fluoride or fluosilicate ionsacts as an activator and/or anti-depressant for neutralizing the effectof the depressants used in the,

process prior to the flotation of the niobium bearing minerals.

In accordance with the present invention, separation of theniobium-bearing minerals from their gangue is accomplished either byconditioning the feed with a depressant for the niobium-bearingminerals, floating ofi? the bulk of the gangue in single or stageoperations, recovering the magnetic-iron minerals and the micas ifdesired, and conditioning the remaining ore with the above noted novelreagent combination that promote an effective and selective flotation ofthe niobium minerals, more particularly the pyrochlore; or byconditioning the feed for floating off the niobium-bearing mineralsalong with the bulk of the oxides and silicates, rejecting as tailingsthe bulk of the carbonate content, recovering from this bulk concentratethe micas and magnetic minerals if desired, and submitting the residualconcentrate to the seinvolved in the process for treating ore high incarbonate content, the bulk of this carbonate gangue being rejected as atailing when floating off a bulk silicate-oxide concentrate, as apreliminary concentration step.

Although not a part of the present invention, if the feed is a naturalore, a careful preparation before flotation is usually found advisable.As shown in the drawings, this comprises grinding and classification orother wise reducing the ore to a suitable size for froth flotation feed,normally to about minus 35 mesh and preferably minus 50 or minus 60mesh. Any combination of crushing, grinding and classification steps maybe used.

If the ore has more than about 10% by weight of carbonates andphosphates, the procedure outlined in Figure 1 or 3 will be preferablyfollowed. If the ore has less than about 10% by weight of carbonates andphosphates and has a high silicate content, the procedure outlined inFigure 2 is preferred. In accordance with the procedure illustrated byFigure 1, after the feed has been prepared as outlined above, the groundpulp is conditioned with niobium minerals depressants and acalcite-apatite promoter. This conditioning step is carried out at highsolids although it may be done at flotation density if so desired. Theniobium mineral depressant may be either caustic starch or an alkalisilicate. Such a depressant is necessary because some or part of theniobium minerals react the same as calcite and apatite to most anionictype promoters. It is necessary, therefore, that a depressant be foundof one constituent or the other.

The caustic starch actually comprises a mixture of an alkali such assodium hydroxide and starch. Preferably, it is fed as a solutioncontaining about -10% dissolved solids. The alkali-starch ratio may varyfrom as little as about 1:3 to as high as 3:1.

A suflicient amount should be used to produce depression of theniobium-minerals, the solution being added and conditioned with the pulpfor sufficient time to ensure thorough dissemination.

It has been found also that successful results are readily obtainedusing a water-soluble silicate as niobiummineral depressant. Usually,the amount of silicate required is about 1 to 3 pounds per ton of feed.

Other depressants may be used but these two groups have been found to bethe most effective.

The time of conditioning will depend on the characteristics of theparticular ore being treated, usually about 5 minutes are suflicient.

Either concurrently with or subsequently to this operation, an anionicpromoter for calcite and apatite is added. This promoter may be one ofseveral types; a fatty acid such as oleic, stearic, palrnitic, fish-oilfatty acids, cocoanut oil fatty acid, and the like, or soaps thereof, aswell as the various commercial mixtures thereof and naphthenic acids ortheir soaps. Such naturally occurring mixtures of fatty and resin acidssuch as talloel or residue such as cotton-seed-foot oil or their soapsare also satisfactory, as well as sulphonated reagents such assulphonated higher aliphatic alcohols, sulphonated fatty acids.Sulphonated petroleum hydrocarbons may also be used per se or inconjunction with another promoter; cottonseed-foot oil has been found togive excellent results in conjunction with a petroleum sulphonate andsince it is readily available and inexpensive, is perhaps preferable.

In general, the amount of promoter required is about 1.5 to 3.0 lb./ton.Excessive amounts over that should necessarily be avoided as tending toovercome the effect of niobium minerals depressant and to increase thelosses in the subsequent flotation.

If conditioning was at high solids the pulp is first reduced toflotation density of from 15-25% solids before being subjected toflotation, which is carried until the calcite and apatite removal isapparently complete.

The addition of a small quantity of frother to the flotation cell isusually beneficial during this operation. Stage addition of reagents tothe flotation circuit is often useful to assure complete removal of thecalcite and the apatite.

The condition and flotation procedures are usually advantageouslyrepeated in sustained commercial operations taking off a secondcalcite-apatite concentrate or middling product, to assure the mosteconomical complete removal of these minerals.

These calcite-apatite concentrates are usually combined and subjected toa cleaner and recleaner flotation. A small addition of niobium mineralsdepressant, about 1.0/lb./ton is usually beneficial in these cleaningoperations. As the object of these cleanings is to reduce the niobiumlosses encountered in the bulk flotation of calcite and apatite, thecleaner tails, which are enriched in Nb O are recycled to the originalflotation feed, or to any other point in the circuit which might befound more advantageous, like the classification, the conditioning orthe calcite-apatite flotation.

The tailing from this first step of concentration contains most of theNb O contained in the original feed, mixed with some minerals like mica,magnetite, diopside, etc.

This tailing could be treated to recover the mica and the magnetite,which are saleable products or could be fed directly to the niobiummineral flotation.

On account of their commercial by-product values, it is soundeconomically to recover at this stage the mica and the magnetite. Theseminerals can be recovered in that order, but the magnetite can berecovered first if desired.

To obtain the mica concentrate, the machine discharge or tailing fromthe calcite-apatite concentration is decanted or dewatered to remove theexcess and the effect of the reagents used in the preceding flotation.It has been found unnecessary at this stage to use a scrubbing treatmentto effect this reagents removal.

This dewatering can be effected in a large pool classifier or in athickener. The thickened pulp is then conditioned with a mica promoterwhich in thise case is any good cationic promoter of the primary monoamine acetate type such as coco amine, soya amine and the like or of thediamine acetate type such as coco diamine or tallow diamine and thelike. Amine 220, which is a trade name of Union Carbide and CarbonCorporation for 1-hydroxyethyl-2-heptadecenyl glyoxalidine, and Aeromine2026, which is a trademark for an amine cationic flotation reagent ofuncertain'composition made by the American Cyanamid Co., have been foundto give excellent results. In general the amount required is relativelysmall, about 0.4 lb./ton of flotation feed.

At the same time, the niobium mineral depressant is added. Causticstarch, added at the rate of 0.5 to about 1.5 lb./ton has given goodresults at this stage and was used preferably. A slight amount offrother, about 0.05 lb./ ton added to the flotation cell is ordinarilyhelpful to carry this flotation. This mica flotation is a basic circuitin the presence of causticized starch, produces a selective separationof the pyrochlores from the mica, and is an important feature of thisinvention.

As in the case of the calcite-apatite flotation, cleaning of the micaconcentrate with a small addition of niobiumdepressant (about 0.2lb./ton of causticized starch), is advantageous to minimize the niobiumlosses carried over with the mica concentrate. The tailing from thiscleaner operation is either returned at the head of the mica flotation,like at the decantation feed, or at such other point in the circuit thatmight be found more advantageous.

The machine discharge or tailing from the mica flotation could be fed tothe magnetite recovery circuit, if the recovery of this iron concentrateis desired.

The circuit consists of any appropriate drum type or belt type low ormedium intensity wet magnetic concentrator. The magnetite, which ishighly magnetic is attracted by the magnetic field, while the rest ofthe ore is unaflected, making the separation possible.

One or two cleanings of the magnetite concentrate in similar typemagnetic separators is advisable to raise the grade of the magnetiteconcentrate to saleable grade and to liberate the non-magnetic oreparticles mechanically trapped between the magnetite grains during theseparation process. These cleaner tails are again returned to the headof this circuit or by-passed directly with the magnetite tailings to thefollowing operation stage.

At this point, one has reached the stage where the niobium-bearingminerals (the pyrochlore) can be directly floated oflf into a high gradeconcentrate.

As stated previously, the feed to the pyrochlore flotation could beeither the calcite-apatite flotation tailings, bypassing the mica andthe magnetite removals, or the tailings from the mica flotation, or thetailings from the magnetic separation.

If the mica flotation is by-passed, the pyrochlore flotation can proceedwith the addition of a specific mica depressant, like one of the arabicgums such as guar gum, guartex and the like, a glue, starch or any otherappropriate mica depressant fed at the rate of about 0.5 lb./ton. Themica flotation is delayed this way but not enough to produce a one passclean separation of the pyrochlore from the mica, and three or foursuccessive pyrochlore concentrate cleanings are required to bring outthe optimum pyrochlore concentrate grade.

The pyrochlore flotation procedure is not modified whether the magneticseparation is performed or not. The tailing or reject from the previousconcentration operation is decanted or dewatered to remove the eflectand the excess of the reagents already used in previous operations.

This thickened pulp is then conditioned for the niobium mineralsflotation. Heavy solid (50% solid) conditioning, though preferable, isnot absolutely required, and dilution of the pulp to flotation density,about 25% solid can be eflected before or after the conditioning.

Where conditioning at high solids, or even conditioning prior toflotation cannot be employed, it is possible to add the reagentsdirectly to the flotation cell. This practice is undesirable and'shouldbe avoided if possible, since it requires more reagent and/ or longertreatment in the cells, and even then is not as satisfactory. It is alsoan advantage of the present invention that it permits the use ofreadily-available cationic-type promoters such as described in the micaflotation.

The amount of promoter used will vary with the nature of the ore, theWater conditions, i.e. temperature, acidity, hardness, etc., of thewater and the average particle size mineral and content of the feedbeing treated. In general an amount ranging from 0.5 to 1.5 lbs ./ton ofore treated is necessary. In some cases, a frother may be useful. Wherea frother is desirable, any suitable type such as pine oil, cresylicacids and the commercial higher alcohol frothers may *be used.

Of primary importance is also the use of the novel activator andselectivity-assisting agent for the pyrochlore minerals, of thisinvention. This activator may also act as an antidepressant toneutralize the depressing effect of the reagents used inthe prior stepsof the process de scribed: such as causticized starch, sodium silicates.or others. This activator should be anefiectivesource of fluoride and/orfluosilicate ions. The particular source may be varied. The necessaryions may be provided, for example, per se or as a soluble salt thereof.-Where the circuit itself is not normally acidic (pH lower than 7) itshould be made so. This may be done by adding an acid such as HF, H SiFIt may also be done by adding a soluble fluosilicate such as that ofsodium or potassium, since these salts have an acid reaction. Similarly,a combination of a mineral acid, sulfuric, hydrochloric or the like maybe used with a soluble fluoride or acid fluoride such as those ofsodium, potassium or ammonium.

As to the amount of activator used, the demand may be quite flexible. Ingeneral it will vary between 2 to 6 lbs/ton of feed.

Good results were obtained by adding about 2 lbs./ ton in the initial'conditioning or to the cells during the rougher flotationpreconditioning is not used, and small additions stage fed duringflotation and cleaning.

The diluted conditioned pulp is then sent to the rougher flotationcircuit as is shown in Figure I. An excellent separation of thepyrochlores from the rest of the ore is obtained. This rougherconcentrate may be sent to a cleaner flotation, to further upgrade itsNb O assay. The tailing from the cleaner circuit can be recycled to thefeed of the rougher flotation, or at any particular point found mostadvantageous.

If the ore contains a substantial proportion of metallic sulfides,particularly pyrite, it is possible in accordance with the presentinvention to collect a pyrite concentrate without affecting thesubsequent pyrochlore flotation. The feed for the pyrite flotation maybe either the calciteapatite flotation tailings, or the tailings fromthe magnetic separation.

The tailings are conditioned for about 5 minuteswith a Xanthate, in abasic, neutral or acidified circuit. The pyrite is floated and thetailing constitutes the feed for the pyrochlore flotation describedhereinabove.

When the ore to be treated contains only a small proportion of carbonateand phosphates (about 10% and less) and has a high silicate content, thecalcite-apatite flotation may be by-passed as shown in Figure 2.

The prepared feed can be fed directly to the mica flotation and thenceto the magnetic separation and the resultant tailings subjected to thepyrochlore flotation.

It is also possible to subject the prepared feed only to the pyrochloreflotation, by-passing both the mica flotation and the magneticflotation; in this case the pyrochlore flotation will be eifected withthe addition of a specific mica depressant such as guar' as describedhereinabove with respect to Figure 1.

In accordance with the procedure illustrated in Figure 3, thepreliminary concentration step consists in floating oif the bulk of thesilicate and oxide content of the ore, along with the niobium-bearingminerals, and discarding most of the carbonate and phosphate content asflotation tailings. This bulk silicate-oxide concentrate is similar incomposition to the product previously referred to as The tailing fromthe first step of concentration, containing most of the Nb O containedin the original feed, mixed with some minerals like mica, magnetite,diopside, etc, and is processed to obtain the final niobium concentrate,the same way as'described in discussing the process illustrated inFigure 1, for mica, magnetite and sulfides, optional removal, andniobium minerals flotation.

After the feed has been adequately prepared, the ground pulp isconditioned for about 2 minutes With a cationic collector or promoter ofthe same family referred to in the mica and niobium-mineral flotations.This conditioning is usually performed at high solids (i50% solids)although it may be done at flotation density if so desired.

Usually, the amount of collector required is about 1 to 3 pounds per tonof feed.

If conditioning was at high solids, the pulp is first reduced toflotation density of from 15-25% solids before being subjected toflotation, which is carried until the silicates and oxide removal isapparently complete.

Staged addition of reagents to the flotation circuit is often useful;conditioning and flotation procedures can be advantageously repeated insustained commercial operations taking off a second silicate-oxideconcentrate, to assure the most economical complete removal of theseminerals, particularly the pyrochlores.

The residue from this flotation is the calcite-apatite concentrate,while the concentrate contains most of the niobium minerals and isfurther processed for niobium recovery the same way as the residue fromthe calciteapatite flotation was treated in the discussion of theprocess illustrated by Figures 1 and 2.

This invention may be illustrated in conjunction with the followingexamples, which are illustrative only and not by way of limitation. Allparts are by weight unless otherwise noted. 7

7 EXAMPLE 1 Calcite-apatite flotation-Mica flotation-Magneticseparation-Pyrchl0re flotation A sample of ore from the Oka district,Province of Quebec, Canada, comprising pyrochlore with a ganguecontaining mainly calcite, apatite, mica, pyroxene, magnetite and pyritewas given a preliminary treatment by crushing and grinding to minus 65mesh.

A pulp of the ore comprising about 50% solids in water was conditionedfor minutes with 0.8 lbs/ton of oleic acid, 1.2 lbs./ ton of Petronate L(a trademark of L. Sonneborn Sons Inc., New York City for a salt of apetroleum sulfonic acid), and 2 lbs/ton of water glass (sodiumsilicate).

This conditioned pulp was then reduced to about 20% solids, thecalcite-apatite concentrate floated, and the concentrate was cleanedwith 1 lb./ ton of sodium silicate. The cleaner tails were combined withthe flotation tails.

These tailings were dewatered to about 60% solids and conditioned 5minutes for mica flotation with 1.0 lb./ton of causticized starch havingan alkali-starch ratio of 1 to 3 and 0.5 lb./ ton of Amine 220. Theconditioned pulp was then diluted to about 20% solids, and the micaconcentrate floated off. This concentrate was cleaned twice with theaddition of 1.0 lb./ton of causticized starch to the cleaner cells.

The cleaner tails were combined with the flotation tails and treated bymagnetic concentration to recover a magnetite concentrate, which wasgiven one cleaning pass.

The cleaner tails and the tailings from the magnetic concentration weredewatered to about 60% solid and conditioned 6 minutes with 4.0 lb./tonof HF, and 0.5 lb./ton of Aeromine 2026. The conditioned pulp wasreduced to about 20% solid and the pyrochlore concentrate floated off.This concentrate was given two cleanings with the addition of 0.5lb./ton of HP at each cleaning.

The two cleaner tails were combined for assaying.

The results obtained are shown in the following Table I.

These results indicate that this process permits an economical recoveryof a high grade pyrochlore concentrate, containing 29.5% Nb O andrepresenting an estimated overall recovery of better than 70%. It alsopermits the production of mica and magnetite concentrates as commercialby-products, and this with acceptable Nb O losses.

EXAMPLE II The whole ore was treated as in the Example I to remove acalcite-apatite concentrate, followed by magnetic concentration toremove a magnetite concentrate, and then the dewatered combined tailingsand cleaner tails were conditioned directly for the pyrochloreflotation, bypassing the mica flotation.

The reagents used in the pyrochlore flotation conditioning were HF at 3lbs/ton, Aerornine 2026 at 0.8 lb./ton, and guar at 0.5 lb./ ton tofavor the mica depression. The pyrochlore concentrate was cleaned threetimes and the cleaner tails combined for assaying. This procedure gavethe following results:

The whole ore was treated as in Example I to remove a calcite-apatiteconcentrate and the dewatered tailings from this flotation wereconditioned directly for the pyrochlore flotation, bypassing the ironand mica removals.

The reagents used in the pyrochlore flotation conditioning were HP at 5lbs/ton, Amine 220 at 0.6 lbs./ ton, and guar gum at 0.4 lbs/ton tofavor the mica depression.

The pyrochlore concentrate was cleaned twice only with the addition of0.2 lbs/ton of guar gum and 0.4 lbs/ton of Amine 220 to the cleanerflotation, and the cleaner tails combined for assaying.

The results obtained through this procedure are tabulated in Table III.

Table III Percent Percent Distribution, Products Weight Nbgos PercentNbzos Calcite-apatite concentrate- 70. 1 0.06 9. 5 Pyrocliloreconcentrate 1. 2 22. 6 61. 8 Cleaner tails 1. 8 1. 8.0 Tailings 26. 9 0.34 20. 7 Feed (calculated) 100.0 0. 44 100. 0

These results indicate clearly the possibility of a successful selectiveconcentration of the pyrochlore directly after the removal of thecarbonaceous constituents of the ore.

The grade of 22.6% Nb O can be improved with successive cleaningoperations.

EXAMPLE IV The whole ore was treated as in Example I to remove acalcite-apatite concentrate, followed by magnetic concentration toremove a magnetite concentrate. The tailings from this concentrationwere conditioned for 5 minutes with a xanthate (0.5 lbs./ton of Z-6, anamylxanthate from Dow Chemical), and 1.0 lbs/ton of sulfuric acid, forthe removal of metallic sulfides, particularly pyrite. The dewateredtailings from this flotation were then conditioned with the samereagents, as used in Example II; the pyrochlore concentrate was cleanedonly once. This procedure gave the following results.

These results are indicative that very good concentration of thepyrochlore can be effected, after metallic sulfides recovery, if such arecovery is found desirable.

More cleanings of the pyrochlore concentrate would be necessary toup-grade this concentratelto above 20% Nb O 2 EXAMPLE V A pulp of theore comprising about 50% solids in water was conditioned for 2 minuteswith 1.0 lbs/ton of Aeromine 2026 and 0.5 lbs/ton of Amine 220. Thisconditioned pulp was then reduced to about 25% solids, and the silicateand oxide minerals, together with the niobium minerals floated ofl.

Staged addition of collectors to the flotation cell at the rate of 0.3lbs/ton of each of the collectors: (Aeromine 2026 and Amine 220) wasmade to ascertain the com-- plete collection of the niobium minerals.

The tailings from this flotation contained mostly the calcite and theapatite and was rejected as a calcite-apatite residue.

The concentrate so obtained contained most of the niobium minerals andwas further treated for the optimum concentration of these minerals.

This concentrate was dewatered to about 50% solids and submitted to micaflotation the same way as described in Example I.

The mica-flotation tailing was then submitted directly to the selectivepyrochlore flotation as also described in These results indicate thatthis process permits an economical recovery of a high grade pyrochloreconcentrate, containing 30.5% Nb O and representing an estimated overallrecovery of better than 71% EXAMPLE VI The whole ore was treated as inExample V, the cationic collectors being added at the rate of 0.6lbs/ton of Amine 220 and 1.5 lbs/ton of Aeromine 2026. This combinationof reagents gave better frothing characteristics to the flotation.

The mica was removed and the pyrochlore flotation proceeded with as inExample V.

The results obtained are shown in the following table:

Table VI Percent Percent Distribution,

Products Weight Nbgos Percent Feed 100. 0. 55 100. O CaL-apatite Residue61. 2 0. 03 3. 3 Mica Concentrate 11. 1 0.55 11.1 PyrochloreConcentrate. 1. 1 34. 3 68. 3 Pyrochlore OL-Tails 2.0 1. 70 6. 2Tailings 24. 6 0. 25 11. 1

These results indicate an overall estimated recovery of about 72% in aconcentrate containing 34.3% Nb O This method of processing can thenproduce a successful selective concentration of the pyrochlore.

From these results it will be seen that not only is the process of thepresent invention adapted to produce satisfactory high gradeconcentrates, with high recovery, but it is well adapted for continuousoperation.

We claim:

1. A process for beneficiating a mixture of minerals comprising a lowconcentration of oxidized niobium minerals dispersed in a large amountof gangue, said mixture being ground to particle sizes suitable forfroth flotation feed, which comprises forming an aqueous pulp of saidmixture, subjecting said aqueous pulp to froth flotation in the presenceof a cationic promoter of the aminetype and a selective activator forthe niobium-bearing mineral selected from the group consisting offluoride and fluosilicate ions, and collecting the resultantniobium-rich flotation concentrate, separately from the niobium-poorflotation tailing.

2. A process as claimed in claim I, wherein the aqueous pulp subjectedto froth'flotation is at a pH lower than 7.

3. A process as claimed in claim 1, wherein a frother is added to theaqueous pulp.

4. A process as claimed in claim 3, wherein said frother is selectedfrom pine oil, cresylic acid and higher alcohols.

5. A process as claimed in claim 1 wherein said cationic promoter isselected from monoamine and diamine acetate and heterocyclic organicamines.

6. A process as claimed in claim 1, wherein said gangue includes micaand wherein a mica depressant is added to the aqueous pulp subjected tofroth flotation.

7. A process as claimed in claim 6, wherein said mica depressant isselected from gum arabic, gum guar, glues and starch.

8. A process as claimed in claim 1, wherein said gangue includes asubstantial amount of calcite and apatite, including the preliminarysteps of subjecting the aqueous pulp to flotation in the presence of ananionic promoter selected from the group consisting of the higher fattyacids, resin acids, naphthenic acids, mixtures thereof, their soaps,sulphonated petroleum hydrocarbons and higher aliphatic alcohols, and adepressant selected from the group consisting of caustic starch and analkali silicate, collecting the resultant flotation concentrate as acalciteapatite concentrate substantially from from niobium bearingminerals, separaely collecting the residual tailing as a concentrate ofniobium-bearing mineral substantially free from apatite and calcite, andusing said last named concentrate as the feed for the froth flotation ofthe niobium-bearing minerals.

9. A process as claimed in claim 8, wherein the caustic starch is amixture of starch and an alkali, the alkalistarch ratio being betweenabout 1:3 and 3: 1.

10. A process as claimed in claim 1, wherein said gangue includes asubstantial amount of mica, including the preliminary steps ofsubjecting the aqueous pulp to froth flotation in the presence of acationic promoter of the amine type and of caustic starch as a niobiummineral depressant, collecting the resulting flotation concentrate as amica concentrate substantially free from niobiumbearing minerals andseparately collecting the residual tailing as a concentrate ofniobium-bearing minerals substantially free from mica, and using saidlast named concentrate as the feed for the froth flotation of theniobiumbearing minerals.

11. A process as claimed in claim 1, wherein said gangue includes asubstantial amount of magnetic minerals, the preliminary steps ofsubjecting the aqueous pulp to a magnetic separation, collecting aconcentrate having a high iron assay and separately collecting theresidual tailing as a concentrate of niobium-bearing mineralssubstantially free of magnetic minerals, and using said tailing as thefeed for the froth flotation of the niobium-bearing minerals.

12. A method of beneficiating ores o-f niobium-bearing minerals, moreparticularly pyrochlores, containing excessive amounts of ganguematerial, which comprises the steps of reducing the ore to suitable sizefor flotation feed, conditioning the pulp with an effective amount of ananionic type promoter selected from the group consisting of the higheraliphatic fatty acids, resin acids, naphthenic acids,cotton-seed-foot-oil, oleic acid, mixtures thereof and their soaps,sulphonated petroleum hydrocarbons, higher aliphatic alcohols, andmixtures thereof, and an effective amount of niobium-bearing mineraldepressant selected from causticized starch and alkali silicates,subjecting the conditioned pulp to froth flotation to floatsubstantially all the carbonate and phosphorus bearing mineralstherefrom, collecting and dewatering the resultant tailings,conditioning an aqueous pulp of these tailings with an effective amountof a substance selected from caustic starch and alkali silicates andwith a cationic type promoter selected from primary monoand di-amineacetates, subjecting the conditioned pulp to froth flotation to remove amica concentrate, collecting the resultant tailings and subjecting themto magnetic separation to collect a magnetite concentrate, collectingand dewatering the resultant tailings, conditioning an aqueous acidicpulp of these tailings with an effective amount of cationic promoter forthe niobiumbearing minerals selected from the same group from which themica flotation promoter was selected and an effective amount ofactivator selected from the group consisting of fluoride andfluosilicate ions, subjecting the conditioned pulp to froth flotation,and collecting the resultant flotation concentrate as a high gradeniobium concentrate.

13. A process as claimed in claim 1, wherein said gangue includes asubstantial amount of calcite and apatite, including the preliminarysteps of subjecting the aqueous pulp to flotation in the presence of acationic promoter selected from the group consisting of cationicpromoters of the primary mono amine acetate type, of the di-amineacetate type and of the heterocyclic amine type, collecting theresultant flotation concentrate as a niobium-bearing mineral, silicateand oxide concentrate substantially free from calcite and apatite, andusing said last named concentrate as the feed for the froth flotation ofthe niobium-bearing minerals.

14. A method of beneficiating ores of niobium-bearing minerals, moreparticularly pyrochlores, containing an excess amount of ganguematerial, which comprises the steps of reducing the ores to suitablesize for flotation feed, conditioning the pulp with an eflective amountof cationic promoter of the amine type, subjecting the conditioned pulpto froth flotation to float a concentrate containing substantially allthe niobium-bearing minerals together with silicates and oxides andsubstantially free from all the carbonate and phosphorus bearingminerals,

, collecting said concentrate, conditioning an aqueous pulp of saidconcentrate with an effective amount of a substance selected fromcaustic starch and an alkali silicate and with a cationic promoterselected from primary mono and di-amine acetates and heterocyclicorganic amines, subjecting the conditioned pulp to froth flotation toremove a mica concentrate, collecting the resultant tailings andsubjecting them to magnetic separation to collect a magnetiteconcentrate, collecting and dewatering the resultant tailings,conditioning an aqueous acidic pulp of these tailings With an effectiveamount of cationic promoter for the niobium-bearing minerals selectedfrom the same group from which the mica flotation promoter was selectedand an effective amount of an activator selected from the groupconsisting of fluoride and fluosilicate ions, subjecting the conditionedpulp to froth flotation, and collecting the resultant flotationconcentrate as a high grade niobium concentrate.

15. A process as claimed in claim 1, wherein said gangue includes asubstantial amount of metallic sulphides, including the preliminarysteps of subjecting the aqueous pulp to froth flotation in the presenceof a promoter of the Xanthate type, collecting the resultant flotationconcentrate as a metallic sulphide concentrate essentially free fromniobium-bearing minerals and separately collecting the residual tailingsas a concentrate of niobium-bearing minerals substantially free frommetallic sulphides, and using said last named concentrate as a feed forthe froth flotation of the niobium-bearing minerals.

References Cited in the file of this patent UNITED STATES PATENTS OMearaOct. 6, 1942 Last et al. Mar. 3, 1952 12, pp. 17, 24 and 44.

UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No,2,959,281 November 8, 1960 J, A. Roland Faucher et a1.

It is herebycertified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

In the grant (only) line 1, name of first inventor, for J. A, RolandFucher" read J. A. Roland Faucher in the printed specification, column4, line 10, after "like" insert to line .32, for "thise" read this line49, for "is" read in column 10, line 38, for "from" first occurrenceread free line 39, for "separaely" read separately Signed and sealedthis 2nd day of May 1961.,

(SEAL) Attest:

ERNEST W9 SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents

1. A PROCESS FOR BENEFICIATING A MIXTURE OF MINERALS COMPRISING A LOWCONCENTRATION OF OXIDIZED NIOBIUM MINERALS DISPERSED IN A LARGE AMOUNTOF GANGUE, SAID MIXTURE BEING GROUND TO PARTICLE SIZES SUITABLE FORFROTH FLOTATION FEED, WHICH COMPRISES FORMING AN AQUEOUS PULP OF SAIDMIXTURE, SUBJECTING SAID AQUEOUS PULP TO FROTH FLOTATION IN THE PRESENCEOF A CATIONIC PROMOTER OF THE AMINE TYPE AND A SELECTIVE ACTIVATOR FORTHE NIOBIUM-BEARING MINERAL SELECTED FROM THE GROUP CONSISTING OFFLUORIDE AND FLUOSILICATE IONS, AND COLLECTING THE RESULTANTNIOBIUM-RICH FLOTATION CONCENTRATION, SEPARATELY FROM THE NIOBIUM-POORFLOTATION TAILING.